Change of Molecular Polarizability Density and Nature of the Smectic A – Crystal B Phase Transition of Liquid Crystal 2O.2C

AbstractComponents of the molecular polarizability density (Gj = γj/v) for light waves polarized along (j = ||) and across (j = ) the optical axis of uniaxial liquid crystal are related to the components of polarizability (γj) and the volume per molecule in the medium (v). In this work, the dependences of Gγ (components Gj, mean value Gm and anisotropy Gα) on temperature and light wavelength (λ) were determined for smectic A and crystal В phases of liquid crystalline ethyl-p-(4-etoxybenzylideneamino)cinnamate. The temperature dependences of the effective wavelengths (λγ) for electronic transitions which are responsible for dispersion Gγ(λ) in the visible range were obtained in both phases. The relation between the values of λγ and the characteristics of real electronic transitions (wavelengths, oscillator strengths and polarizations) and the orientational order parameter (S) of molecules was established. Using the values Gγ and λγ it was revealed that the smectic A – crystal B phase transition is accompanied by very small change of S, decrease in the anisotropy of molecular polarizability and change of the polarization of electronic transitions.